Rechargeable batteries produce energy from electrochemical reactions. In typical rechargeable batteries, the battery is designed to deliver optimal performance at or close to room temperature. Extreme high or low temperatures may compromise the performance and/or life of the battery. In order to address the performance issues at extreme temperatures, batteries may integrate heating and/or cooling systems, which adds volume, weight, complexity and cost. In many cases, this may limit the use of batteries for applications in extreme temperature environments.
Recently, rechargeable batteries have been designed with cells having a specific combination of anode, cathode, and electrolyte compositions to maintain long cycle life at high temperatures while also delivering power at low temperatures. For example, Cho, in WO 2013/188594, incorporated herein by reference for all purposes, discloses an electrolyte formulation comprising a first additive containing a sulfonyl group for use in rechargeable batteries. As disclosed by Cho, the use of additives containing sulfonyl groups in the electrolyte may provide a battery which maintains cycle life at high temperatures and delivers power at low temperatures, significantly reducing the need for thermal management systems.
Cho specifically discloses a rechargeable battery comprising a nonaqueous electrolyte solution comprising a lithium salt, LiPF6, at 0.6-2 M and an organic solvent mixture which includes 35 vol. % ethylene carbonate, 5 vol. % propylene carbonate, 50 vol. % ethyl methyl carbonate, and 10 vol. % diethyl carbonate, and at least one additive containing a sulfonyl group, ethylene sulfite, at 0.1-5 wt. % and vinylene carbonate at 0.2-8 vol. %. The electrolyte formulation provided by Cho provides an increase in power for cold cranking an engine as compared to lead acid batteries and maintains long cycle life at high temperatures.
The use of the additive containing the sulfonyl groups in addition to the vinylene carbonate in organic electrolyte provides a stable, lower impedance rechargeable lithium ion battery. The additive containing the sulfonyl group may lower impedance by reacting with the anode to create a stable solid electrolyte interface (SEI) that is more ionically conductive than with an electrolyte without the additive. In addition, the vinylene carbonate may be efficient at passivating the carbon-based anode during initial charging making the SEI less soluble, and thus, may reduce decomposition of the sulfonyl additive.
However, the inventors herein have recognized that an improved electrolyte formulation based on the electrolyte disclosed by Cho may be provided to improve extreme temperature performance and reduce gassing. An electrolyte formulation comprising a first additive containing a sulfonyl group, an anti-gassing agent, a second additive, and a salt system is provided. Further, the formulation includes vinylene carbonate and a solvent system. The electrolyte formulation may be used in various cell constructions, but may be specifically beneficial in a pouch construction due to the reduced gassing.
The disclosed electrolyte formulation may reduce gassing over a wide temperature range during cycling. Further, the ratio between the sulfonyl group additive and vinylene carbonate may be controlled to maintain an improved SEI layer for improved cell cycling efficiency. As provided herein, the optimized electrolyte formulation reduces/maintains impedance and provides improved power during cold crank, while also reducing gassing during high temperature cycling and/or storage.
As provided herein, the first additive containing a sulfonyl group may be 0.1 to 5 weight % of the electrolyte formulation. The anti-gassing agent may be equal to or less than 2 weight % while the second additive may be 0.1-5 weight % of the electrolyte formulation. The additional additive may be chosen to reduce the loading of the vinylene carbonate while still maintaining good SEI development. The salt system may comprise a lithium salt combined with a co-salt, wherein the co-salt is unlikely to generate Lewis acidic decomposition.
It will be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.